Vacuum skin packaging

ABSTRACT

Disclosed are packages and methods for packaging perishable foods such as meat, fish, poultry, vegetables or other food products. The packaging comprises a vacuum skin package comprising a film having specific package gas permeability requirements and a framing element within which the packaged goods are held.

This application claims the benefits of U.S. Provisional Application60/552,268, filed Mar. 11, 2004, the entire disclosure of which isincorporated herein by reference.

The invention relates to packaging, to packaging for containing meat,fish, poultry, vegetables or other food products, and to method forpackaging goods using this improved packaging.

BACKGROUND OF THE INVENTION

Perishable goods are subject to exposure to and contamination bymicrobial organisms such as bacteria, molds and the like by contact withairborne organisms or by contact with organisms on surfaces. Thecontamination can result in accelerated spoilage, toxin formation andother harmful effects. Thus it is desirable to protect the goods fromcontact with microbial organisms. Packaging such perishable goods in gasimpermeable materials such as foil, paperboard and oxygen barrier filmscan provide a barrier to microbial contamination.

However, an anaerobic organism such as Clostridium botulinum produces apotent toxin that is the causative agent of botulism, an extremelyvirulent, dangerous, food poisoning. Since C. botulinum is an anaerobe,gas impermeable materials such as foil, paperboard and oxygen barrierfilms may not be suitable to package goods highly susceptible to botulintoxin formation. Spores of C. botulinum are heat resistant; it isimpossible to kill the spores by merely heating the food. It isnecessary to provide a package that allows oxygen to contact the surfaceof perishable goods to minimize the growth of C. botulinum. Thus,packages for fresh fish must provide a physical barrier to microbial andother contamination, yet provide for oxygen permeability.

C. botulinum contamination is particularly problematic in fresh fish.Traditionally, fresh fish has been sold in ice-chilled containers opento the atmosphere to minimize the growth of C. botulinum and consequenttoxin formation. Such sales methods previously have been limited torelatively small geographic areas near the bodies of water where thefish were caught. For broader distribution, fish has traditionally beenfrozen.

With modern distribution methods, the desire of consumers in inlandregions to consume fresh rather than frozen fish has increased. However,packaging of fresh fish to minimize the dangers of botulism isdifficult. C. botulinum growth and toxin formation can occur as a resultof time/temperature abuse during processing, storage, and distribution.Potentially hazardous conditions can occur in as little as two hours attemperatures >70° F., 11 hours at 50-70° F., two days at 42-50° F., and7 days at 37.9-41° F.

Typical vacuum packaging inhibits the growth of common spoilageorganisms, but does so under conditions that exclude oxygen andtherefore does not inhibit the growth of C. botulinum. Therefore, vacuumpackaging under conditions that exclude oxygen increases the likelihoodthat botulin toxin may be produced is unacceptable to consumers.

In packaging meat, fish, poultry, vegetables or other food products, itis also desirable to provide for relatively long shelf life of thepackaged goods in a package that does not affect the appearance orkeeping qualities of the packaged goods, is relatively simple andinexpensive to manufacture, yet sufficiently robust to protect thepackaged goods from damage.

Vacuum skin packaging is a common method of packaging many goods wheregoods are tightly packaged within a wrapping material and wheresubstantially all of the atmospheric air is excluded. Often the goodsare placed in a tray or on a board background to increase the rigidityof the package to allow for better merchandising. In some cases, such asfrozen fish, the packaged goods themselves are sufficiently rigid thatadditional rigid packaging elements are not needed.

Packaging has also been known to include certain gases to enhance thekeeping qualities and the shelf life of the contents. Typically thesepackages are made from a plastic material that provides at least apartial barrier to the ingress of unwanted gases. The plastic materialmay be such that it allows gases that may be generated within thepackage to escape. Other known plastic materials allow certain gases topermeate to enhance the keeping qualities of the packaged goods. See,e.g., U.S. Pat. Nos. 4,685,274; 4,840,271; 5,025,611; 5,103,618 and5,115,624. However, the packages disclosed therein can retain only alimited volume of the gas in the headspace.

Some products, such as fresh fish, must be packaged in a film withspecific gas permeability properties to ensure food safety to preventthe growth of anaerobic bacteria. In the case of fresh fish, use of abacking, such as a board, base or tray, is not acceptable because thebacking blocks the oxygen from contacting the fish.

U.S. Food and Drug Administration (FDA) guidance defines that packagingwith “OTR greater than or equal to 10,000 cc/m²/24 hr can be regarded asoxygen permeable”. Such an OTR is unattainable with typical foam traysused in packaging foodstuffs such as fresh meats.

The FDA guidelines also note that “use of an oxygen permeable packagewill not compensate for the restriction to oxygen exchange created bypractices such as packing . . . in deep containers from which the air isexpressed.” If FDA guidelines regarding oxygen permeability are not met,a Hazard Analysis of Critical Control Points (HACCP) plan, a qualityassurance protocol widely used in the food industry, must beestablished. Temperature monitoring is required and time/temperatureindicators (TTI's) must be provided on shipping containers. Whiletemperature controls and monitoring can be accomplished during thedistribution chain, it is impractical to do so after the packaged freshfish has been sold to the consumer. The combinations of time andtemperature that could provide hazardous levels of botulin toxin couldeasily occur during post-sale consumer handling of the packaged freshfish.

It is therefore desirable to develop a vacuum skin package that hasspecific gas permeability and a framing element within which thepackaged goods are held thereby providing sufficient rigidity to thepackage but does not contact the contents (i.e. the packaged goods). Thegoods are in contact only with the gas permeable film, which allows foradequate oxygen to contact the surface of the goods. Packages can bemade with gas impermeable materials if oxygen is available in theheadspace of the package to inhibit growth of anaerobic organisms.However, it is difficult to provide sufficient oxygen in the headspaceof such a package to provide extended protection against growth ofanaerobes.

SUMMARY OF THE INVENTION

The invention includes a vacuum skin package that can contain perishablegoods in which the package comprises or is produced from (a) a firstflexible web of gas permeable skin wrapping plastic material; (b) one ormore rigid or semi-rigid framing elements to surround but not contactthe perishable goods; and (c) a second flexible web of gas permeableskin wrapping plastic material wherein the first flexible web and thesecond flexible web are sealed to each other to contain the perishablegoods. The packages can comprise or be produced from a gas permeableplastic materials having an oxygen transmission rate (OTR) greater thanor equal to 10,000 cc/m²/24 hr.

The invention also include a method of packaging goods comprising (a)placing perishable goods on a first flexible web of gas permeable skinwrapping plastic material in contact with the inside face of the firstflexible web; (b) placing one or more rigid or semi-rigid framingelements in contact with the inside face of the first flexible web tosurround but not contact the perishable goods; (c) placing a secondflexible web of gas permeable skin wrapping plastic material over theperishable goods and one or more framing elements such that the insideface of the second flexible web is in contact with the perishable goods,the one or more rigid or semi-rigid framing elements and the inside faceof the first flexible web; and (d) sealing the first flexible web andthe second flexible web to each other to contain the one or more framingelements and the perishable goods.

Alternatively, the method can comprise (a) placing perishable goods on afirst flexible web of gas permeable skin wrapping plastic material incontact with the inside face of the first flexible web; (b) placing asecond flexible web of gas permeable skin wrapping plastic material overthe perishable goods such that the inside face of the second flexibleweb is in contact with the perishable goods, and the inside face of thefirst flexible web; (c) placing one or more rigid or semi-rigid framingelements in contact with the outside face of the first flexible web andoptionally in contact with the outside face of the second flexible webto surround but not contact the perishable goods; and (d) sealing thefirst flexible web and the second flexible web to each other to containthe perishable goods.

DETAILED DESCRIPTION OF THE INVENTION

The term micron (μ) equals to 1/1000 of a millimeter (mm). A micron issometimes referred to as micrometer (μm). The term mil equals to 1/1000of an inch or to 25.4 microns.

The phrase “inside face” refers to the face of a film or packaging webthat is in contact with the packaged goods and is contained within thepackage after it is formed. The inside face of the packaging web servesas both the food-contact face and the sealant face, because portions ofthe surface of that face are in contact with the food and other portionsof the surface of that face are in the area where seals are made.

The phrase “outside face” refers to the face of a film or packaging webthat is not in contact with the packaged goods and provides the exteriorsurface of the package after it is formed.

The perishable goods can be meat, fish, poultry, fresh vegetables, orcombinations of two or more thereof although other types of goods suchas other foodstuffs can be packaged if desired.

The packaging webs can be prepared from films of thermoplasticcompositions with OTR preferably greater than or equal to 10,000cc/m²/24 hr.

OTR of films are dependent on the thickness of the film and the inherentpermeability of its composition. Permeability is dependent on suchfactors as temperature, relative humidity and pressure of the gasimpinging on the film. Typically OTR is calculated using standardconditions normalized to 23° C., 50% relative humidity and 1 atmosphere.

For good appearance of the package for retail display, it may also bedesirable to use films that are not stretched by the weight of thepackaged goods (i.e. resists creep).

In a first embodiment of this aspect of the invention, the one or moreframing elements are interposed between the first flexible web and thesecond flexible web such that the one or more framing elements are incontact with the inside face of the first flexible web and in contactwith the inside face of the second flexible web to surround but notcontact the perishable goods; and the first flexible web and the secondflexible web are sealed to each other to contain the one or more framingelements and the perishable goods.

In a second embodiment of this aspect of the invention, the one or moreframing elements are in contact with the outside face of the firstflexible web and optionally in contact with the outside face of thesecond flexible web to surround but not contact the perishable goods;and the first flexible web and the second flexible web are sealed toeach other to contain the perishable goods.

Films suitable for the packaging webs can comprise metallocenepolyethylene (mPE) (especially grades with densities less than 0.91g/cc, and more especially grades with densities less than 0.89 g/cc,),which have high OTR.

The metallocene polyethylene (mPE) employed in the present invention canbe any such polyethylene as generally known in the art provided theoxygen permeability is sufficiently high to afford the requisitepermeability necessary for the packaging web. More specifically, themetallocene polyethylene should have a density less than 0.91 g/cc,preferably less than 0.89 g/cc, at which densities the normalizedOTR_(n) at 23° C. and 50% relative humidity will be greater than about12,400 cc-mil/m².day.atm, preferably greater than about 20,000cc-mil/m².day.atm. These mPEs can optionally be blended with other lowcrystalline polyolefin or amorphous polyethylenes (such as low densitypolyethylene, LDPE; linear low density polyethylene, LLDPE; other mPEand the like) provided the blend retains significantly highpermeability. The composition may further comprise ethylene copolymerssuch as ethylene/vinyl acetate copolymers or ethylene/alkyl(meth)acrylate copolymers for improved processing. Also, the compositionmay further comprise ethylene/acid copolymers at least partiallyneutralized with inorganic cations (i.e. ionomers).

For example, a 2-mil thick film of mPE with a density of less than 0.89g/cc and OTR_(n)) greater than about 20,000 cc-mil/m².day.atm will havean OTR of 10,000 cc-mil/m²/24 h.

Compositions comprising ethylene copolymers at least partiallyneutralized with cations (ionomers) and modified with organic acids arealso suitable for preparing films having high oxygen permeability. Thesecompositions are described in greater detail in PCT Patent ApplicationPublication WO03/089240, incorporated herein by reference. Thispublication also describes multi-layer films having high oxygenpermeability, particularly multi-layer films comprising at least onelayer of modified ionomer and at least one layer of mPE.

An ethylene copolymer is a polymer that can comprise repeat unitsderived from about 5 to about 50%, or about 10 to about 19%, or 12 to15%, by weight (wt %) of a polar monomer such as acrylic acid, alkylacrylic acid, or alkyl acrylate, or combinations of two or more thereof,based on the total weight of the ethylene copolymer. The alkyl group maycontain up to about 20 carbon atoms such as methyl, ethyl, butyl,isobutyl, pentyl, hexyl, and combinations of two or more thereof.

An ethylene copolymer may comprise up to 35 wt % of an optionalcomonomer such as carbon monoxide, sulfur dioxide, acrylonitrile; maleicanhydride, maleic acid diesters, (meth)acrylic acid, maleic acid, maleicacid monoesters, itaconic acid, fumaric acid, fumaric acid monoester, asalt of these acids, glycidyl acrylate, glycidyl methacrylate, andglycidyl vinyl ether, and combinations of two or more thereof.

The acid moiety of an ethylene copolymer may be neutralized with acation to produce an ionomer. The neutralization, for example, can rangefrom about 0.1 to about 100, or about 10 to about 90, or about 20 toabout 80, or about 20 to about 40 percent, based on the total carboxylicacid content, with a metallic ion. The metallic ions can be monovalent,divalent, trivalent, multivalent, or combinations of two or morethereof.

The ionomer can also be a blend of an ionomer having a greater than 20%neutralization and, for example, an ethylene (meth)acrylic acidcopolymer to achieve the desired degree of neutralization.

Examples of ethylene copolymers include, but are not limited to,ethylene/methyl acrylate (EMA), ethylene/ethyl acrylate (EEA), ethylacrylate (EA), ethylene/butyl acrylate (EBA), ethylene/isobutylacrylate/methacrylic acid, ethylene/methyl acrylate/maleic anhydride,ethylene/butyl acrylate/glycidyl methacrylate (EBAGMA) andethylene/butyl acrylate/carbon monoxide (EBACO), and butylacrylate (BA).

Examples of commercially available ethylene copolymers include thoseavailable from E. I. du Pont de Nemours and Company (DuPont),Wilmington, Del., carrying the trademarks of Surlyn®, Nucrel®, Appeel®,Bynel®, and Elvaloy®, and Elvax®

The making of the film, multi-layer film, and corresponding filmstructures can be by any such method as practiced in the art. As such,the film and film structures can be typically cast, extruded,co-extruded and the like including orientation (either axially orbiaxially) by various methodologies (e.g., blown film, bubbletechniques, mechanical stretching or the like, or lamination). Variousadditives as generally practiced in the art can be present in therespective film layers including the presence of tie layers and thelike, provided their presence does not substantially alter theproperties of the permeable film or film structure. Such additives cancomprise antioxidants and thermal stabilizers, ultraviolet (UV) lightstabilizers, pigments and dyes, fillers, anti-slip agents, plasticizers,other processing aids, and the like.

The packages comprise two gas permeable film webs. The two film webs aretypically two individual sheets of film. The webs may consist ofidentical compositions and appearance. Alternatively, one web may bedifferent than the other web. For example, one web may be clear,allowing visualization of the packaged goods and the other may be opaqueand/or colored to provide a background. One or both of the webs may alsobe printed with designs, logos, alphanumeric text and/or the like toprovide a pleasing appearance for the package and/or to provideinformation to the consumer. One skilled in the art can appreciate thata single web of film may be folded onto itself to provide two overlyingwebs, or a tube of film may be formed such that two overlying portionsof the tube provide the equivalent of two webs of film.

Packages can be prepared from two webs of gas permeable packaging film.After placing the contents of the package between the film webs andapplying a vacuum, the package is formed by adhering, preferably by heatsealing, the perimeters of the two webs to each other. The heat sealedperimeter of the package can be achieved by superimposing the first andsecond webs of polymeric film and then heat sealing each directly to theother or heat sealing them indirectly through the use of an interveningthird polymeric film, again as generally known and practiced in the art.

The rigid or semi-rigid framing elements may be prepared from paperboardor thermoplastic compositions, such as polyester.

The framing elements are sized so that they surround the goods to bepackaged, but do not contact the goods. For example, but not limitation,the framing elements may define a packaging area from about 10 to about30 cm in length and from about 10 to about 30 cm in width, in which thegoods to be packaged are placed. Although generally described herein interms of rectangular areas, other shapes may be envisioned.

The framing elements may be shaped, embossed, textured and the like toprovide a pleasing appearance for the package. The framing elements mayalso be printed with designs, logos, alphanumeric text and/or the liketo provide a pleasing appearance for the package and/or to provideinformation to the consumer.

One embodiment of the framing element comprises a generally flat, singlepiece of paperboard or thermoplastic composition formed so that itprovides a shaped perimeter margin with a concentric opening therein.This embodiment can contact the flexible packaging web in a generallycoplanar manner, and resembles a mat used in picture framing. The shapedperimeter may be, for example, rectangular. The corners of the perimetermay be square or rounded off. The concentric opening may be of similarshape of smaller dimensions to provide a margin of equal dimensionaround the shape of the framing element. Alternatively, the opening maybe of different shape than the perimeter shape to provide a margin thathas different dimensions depending on the orientation of the openingrelative to the perimeter. Shapes other than rectangular may be used forthe perimeter and/or concentric opening. The thickness of thisembodiment of the framing element may be from about 0.5 mm to about 3mm. The dimensions of the margin may be from about 1 cm to about 3 cm,or greater, depending on the shapes and sizes envisioned for theperimeter and the concentric opening.

An alternative embodiment of the framing element comprises one or moregenerally flat strips of paperboard or thermoplastic composition shapedso that they form portions of a shaped perimeter margin. The strips ofthis embodiment will contact the flexible packaging web in a generallycoplanar manner. For example, two strips with a space between them maybe used to define two sides of a rectangle (e.g. the sides along thelonger dimension of the rectangle), with the distance of the spacebetween the strips providing the dimension of the other two sides (e.g.the sides along the shorter dimension of the rectangle). Alternatively,the strips may define other portions of the perimeter of the packagingarea. For example, a strip may form a portion of a shaped perimetercomprising a corner and portions of two adjacent sides. A strip may forma portion of a shaped perimeter comprising a side, two corners andportions of two adjacent sides. The strips may also be formed so thatthey provide shapes other than rectangular. For example, the strips maybe shaped as arcs, providing curved shapes. The strips may be from about1 cm to about 3 cm wide, or greater, depending on the shapes and sizesenvisioned for the packaging area.

An alternative embodiment of the framing element comprises a strip ofpaperboard or thermoplastic composition formed so that it defines apackaging area that is generally coplanar with the packaging web butalso has a significant dimension in a direction perpendicular to theplane of the packaging web to define a packaging volume.

As disclosed above, the framing elements can be located or placedbetween the two flexible packaging webs to define a packaging area andare sealed within the package. Packages according to this embodiment canbe prepared by (a) placing perishable goods on a first flexible web ofgas permeable skin wrapping plastic material in contact with the insideface of the first flexible web; (b) placing one or more rigid orsemi-rigid framing elements in contact with the inside face of the firstflexible web to surround but not contact the perishable goods; (c)placing a second flexible web of gas permeable skin wrapping plasticmaterial over the perishable goods and the one or more framing elementssuch that the inside face of the second flexible web is in contact withthe perishable goods, the one or more rigid or semi-rigid framingelements and the inside face of the first flexible web; and (d) sealingthe first flexible web and the second flexible web to each other tocontain the one or more framing elements and the perishable goods.

The steps (a) and (b) can be conducted so that (a) occurs before (b),(b) occurs before (a), or simultaneously.

In a second embodiment of the package of this invention, the framingelements are located or placed in contact with the outside face of oneor both of the packaging webs and are on the outside of the package.

An example of this second embodiment comprises a package wherein theframing element comprising a generally flat, single piece of paperboardor thermoplastic composition having a shaped perimeter margin with aconcentric opening therein is adhered to the outside face of one of thegas permeable webs. The framing element may be adhered by meansincluding, for example, hot-melt adhesive or heat sealing.

Alternatively, the framing element comprises a generally flat, singlepiece of paperboard or thermoplastic composition that can be foldedaround the gas permeable packaging webs to provide a shaped perimeterwith an opening. In this example, a portion of the framing element isadhered to the outside face of the first packaging web and a secondportion of the framing element is adhered to the outside face of thesecond packaging web.

Packages according to this embodiment can be prepared by (a) placingperishable goods on a first flexible web of gas permeable skin wrappingplastic material in contact with the inside face of the first flexibleweb; (b) placing a second flexible web of gas permeable skin wrappingplastic material over the perishable goods such that the inside face ofthe second flexible web is in contact with the perishable goods, and theinside face of the first flexible web; (c) placing one or more rigid orsemi-rigid framing elements in contact with the outside face of thefirst flexible web and optionally in contact with the outside face ofthe second flexible web to surround but not contact the perishablegoods; and (d) sealing the first flexible web and the second flexibleweb to each other to contain the perishable goods.

Because the framing element is outside the package, step (c) relating toplacing the framing elements may occur prior to step (a), prior to step(b) prior to step (d), or after step (d); or simultaneously with one ofsteps (a) or (b).

1. A vacuum skin package to contain perishable goods comprising (a) afirst flexible web of gas permeable skin wrapping plastic material; (b)one or more rigid or semi-rigid framing elements to surround but notcontact the perishable goods; and (c) a second flexible web of gaspermeable skin wrapping plastic material; wherein the first flexible weband the second flexible web are sealed to each other to contain theperishable goods.
 2. The package of claim 1 wherein the gas permeableplastic materials have an OTR greater than or equal to 10,000 cc/m²/24hr.
 3. The package of claim 2 wherein the gas permeable plasticmaterials comprise metallocene polyethylene.
 4. The package of claim 2wherein the gas permeable plastic materials comprise ethylene/acidcopolymers at least partially neutralized with at least one cation,modified with at least one organic acid, or both.
 5. The package ofclaim 2 wherein the one or more framing elements are interposed betweenthe first flexible web and the second flexible web such that the one ormore framing elements are in contact with the inside face of the firstflexible web and in contact with the inside face of the second flexibleweb to surround but not contact the perishable goods; and the firstflexible web and the second flexible web are sealed to each other tocontain the one or more framing elements and the perishable goods. 6.The package of claim 2 wherein the one or more framing elements are incontact with the outside face of the first flexible web and optionallyin contact with the outside face of the second flexible web to surroundbut not contact the perishable goods; and the first flexible web and thesecond flexible web are sealed to each other to contain the perishablegoods.
 7. A method of packaging goods comprising (a) placing perishablegoods on a first flexible web of gas permeable skin wrapping plasticmaterial in contact with the inside face of the first flexible web; (b)placing one or more rigid or semi-rigid framing elements in contact withthe inside face of the first flexible web to surround but not contactthe perishable goods; (c) placing a second flexible web of gas permeableskin wrapping plastic material over the perishable goods and the one ormore framing elements such that the inside face of the second flexibleweb is in contact with the perishable goods, the one or more rigid orsemi-rigid framing elements and the inside face of the first flexibleweb; and (d) sealing the first flexible web and the second flexible webto each other to contain the one or more framing elements and theperishable goods.
 8. A method of packaging goods comprising (a) placingperishable goods on a first flexible web of gas permeable skin wrappingplastic material in contact with the inside face of the first flexibleweb; (b) placing a second flexible web of gas permeable skin wrappingplastic material over the perishable goods such that the inside face ofthe second flexible web is in contact with the perishable goods, and theinside face of the first flexible web; (c) placing one or more rigid orsemi-rigid framing elements in contact with the outside face of thefirst flexible web and optionally in contact with the outside face ofthe second flexible web to surround but not contact the perishablegoods; and (d) sealing the first flexible web and the second flexibleweb to each other to contain the perishable goods.